Load damping assemblies are fairly well known in the field, such as those made by Applicant. In such damping assemblies, there are situations or needs in which the damper assembly should be intentionally disabled or “locked out” for reasons of maintenance of a structural system, for example, a tuned mass damper system.
For background purposes, one known version of a hydraulic damper assembly 10 having a lockout function is depicted in FIGS. 1 and 2. This damper assembly 10 is defined by a cylindrical housing 14 that includes a hollow cylindrical tube 16 axially disposed within the interior of the housing 14. The damper assembly 10 includes a moving end 18 that is attached to a load (not shown) and an opposing end 22 that is securably fixed to a support (not shown). A clevis 24, 25 is provided on each of the moving and fixed ends 18, 22 of the assembly 10 to provide attachment capability to each of the load and the support, using spherical bearings 26 provided in each clevis 24, 25. A piston assembly 28 is movably disposed within the confines of the cylindrical housing 14 at the moving end 18 of the assembly 10, the piston assembly 28 including a piston rod 30 and piston 34 that is caused to move though a defined hydraulic chamber 38 provided within the housing 14 and more specifically the interior of the hollow cylindrical tube 16. The ends of the hollow cylindrical tube 16 are secured to a cylinder end assembly 44 that is attached at the fixed end 22 of the damping assembly 10, and a bearing retainer 52 is fixedly attached to the opposing end of the housing 14 at the moving end 18 of the assembly 10.
Upon movement based on an imparted load, a damping force is created when the piston assembly 28 is either extended (loaded in tension) or retracted within the housing 14 (loaded in compression) in which the piston rod is sized to move through a sealed center opening formed in the bearing retainer 52. When in compression, hydraulic fluid is moved through a set of axial orifices 48 formed in the cylinder end assembly 44. This fluid is directed to a spacing 50 that is formed between the outer surface of the hollow cylindrical tube 16 and the interior surface of the housing 14. An accumulator 53 made from foam or other suitable material is provided in the defined spacing or chamber 50, the accumulator 53 spanning an axial portion of the assembly 10. The accumulator 53 is wrapped about the shock tube portion of the assembly with a gap being provided between wrapped ends (not shown)
In tension and as the piston rod 30 is extended, the check valves in the piston head 34 are closed and hydraulic fluid can only be moved to the accumulator chamber 50 through an axial orifice 24 that is formed in the body of the bearing retainer 52. As a result, high dynamic pressure is obtained in the fluid chamber between the piston 34 and the bearing retainer 52. On the other hand and due to movement of the piston 34, the fluid chamber between the piston 34 and the cylinder end assembly 44 draws hydraulic fluid from the accumulator chamber 50 through check valves in the cylinder end assembly 44. As a result, low dynamic pressure is obtained in the fluid chamber between the piston 34 and the cylinder end assembly 44. While in tension, the orifice 24 is at the downstream side of the valve. In normal operation, the adjustment valve is fully open, and therefore the orifice provides the desired damping property. When the adjustment valve is closed, the hydraulic fluid is blocked at the valve and having no place to otherwise go, the damper essentially becomes a rigid strut, producing lock-out in tension.
In compression and as the piston rod 30 is compressed, the check valves in the piston head 34 are open and the check valves in the cylinder end assembly 44 are closed. As a result, hydraulic fluid between the piston 34 and the cylinder end assembly 44 can only be moved through the check valves in the piston head to the fluid chamber between the piston 34 and the bearing retainer 52 and then through an axial orifice 24 that is formed in the body of the bearing retainer 52. As a result, high dynamic pressure is obtained in both the fluid chambers between the bearing retainer 52 and the piston 34. Due to the differential area of the piston, a compressive damping force is obtained. When the adjustment valve is fully closed, the retained hydraulic fluid is blocked by the closed valve and having no place to go, the damper becomes a rigid valve producing lock-out in compression.
According to this version, a lockout sub-assembly 90 is provided at the moving end 18 of the assembly 10. This lockout sub-assembly 90 is specifically defined by a spring-loaded plunger 94 attached to the bearing retainer 52 that can be moved into and out of engagement with the defined axial orifice (not shown). Because the lockout sub-assembly 90 is provided at the moving end 18 of the damper assembly 10, any adjustments are difficult and hazardous to make. In addition, the assembly 10 is limited in terms of operation in that damping is only realized for dynamic (V-squared) loads and not realized for linearly imparted loads.
Accordingly, there is a general need in the field to provide a damping assembly having a more versatile lockout function to enable improved access when this function is desired. It is a further desire to provide a damper having a lockout function that can be effectively used in tension and compression under a variety of load conditions.